A common type of musculoskeletal pain is myofascial pain syndrome, which is pain that emanates from muscles and corresponding connective tissue. Myofascial pain syndrome is often caused by myofascial pain generators called “trigger points.” Trigger points are discrete, focal, irritable spots located in a taut band of skeletal muscle, i.e., a ropey thickening of the muscle tissue. A trigger point is often characterized by a “referred pain” pattern that is similar to the patient's pain complaint. Referred pain is felt not at the site of the trigger point origin, but remote from it. The pain is often described as spreading or radiating. A trigger point develops due to any number of causes, such as sudden trauma or injury to musculoskeletal tissue, fatigue, excessive exercising, lack of activity, tension or stress, and nutritional deficiencies.
A problem in treating myofascial pain syndrome is locating the trigger point, since pain is typically felt remote from the trigger point. A common technique for locating a trigger point is palpation. That is, a physician palpates a muscle region suspected of having a trigger point by applying manual pressure to the region with his finger tips and kneading the muscles. As the physician palpates the muscles, the patient verbally indicates the existence of any pain or sensitivity and whether it increases or decreases as the physician moves his fingers within the suspected region. A shortcoming of this manual technique is that it can only locate a trigger point with a slight degree of certainty, and cannot typically locate the specific muscle that contains the trigger point. In addition, there is no standard unit of pressure to exert when palpitating a muscle, which could lead to a misdiagnosis.
Other techniques to locate trigger points include the use of a palpation index, pressure threshold meters, thermographic measuring devices, and electromyographic identification. However, these techniques are difficult to learn and use and are not always reliable.
U.S. Pat. No. 6,432,063 to Marcus (hereinafter “the Marcus '063 Patent”), the entirety of which is incorporated herein by reference, discloses a method for locating myofascial trigger points (the “Marcus Method”) by applying an electrical stimulus in a suspected muscle area containing a trigger point. As the electrical stimulus is moved about the muscle area, the patient indicates an increase or decrease in the level of pain and sensitivity. Once the maximum pain location has been located, the trigger point has been identified and, thus, it can be treated appropriately. However, the Marcus '063 Patent does not disclose in detail a particular electrical stimulator device that can be appropriately used in connection with the Marcus Method.
There are numerous trans-cutaneous electroneural stimulation (TENS) portable devices available in the marketplace. However, the leads (i.e., the electrodes) of these devices are designed for static and therapeutic purposes, rather than dynamic diagnosis purposes. As a result, TENS devices are not appropriate for locating myofascial trigger points.
U.S. Pat. No. 4,697,599 to Woodley et al. (the “Woodley '599 Patent”) discloses a handheld meter for locating and detecting pain based on the measurement of conductance of skin in the area of perceived pain. The meter includes a housing, two concentric electrodes that extend from the housing, an electrical circuit connected to the electrodes, and a speaker. The electrodes are placed against a patient's skin at the location where a measurement is desired. The electrical circuit generates an electrical signal having a pulse frequency that varies according to the measured conductance of the skin. The conductance is measured aurally by a speaker, which translates the pulses into audible sounds, i.e., “clicks”. The clicks increase in frequency as the conductance of the patient's skin increases, which indicates the location of pain. However, the Woodley '599 Patent does not disclose any correlation between increased conductance and the location of myofascial trigger points; and, therefore, the device is not effective at locating same.
U.S. Pat. No. 5,558,623 to Cody (the “Cody '623 Patent) discloses a therapeutic ultrasonic device, which includes a hammer-shaped applicator having a head with two diametrically-opposed diaphragms. A piezoelectric crystal is connected to each of the diaphragms, which convert electrical energy into ultrasonic energy. The handle is connected electrically (i.e., hard-wired) to a control console, which allows a user to control the operational functions of the applicator, such as frequency, intensity, mode of operation, etc. The Cody '623 Patent relates to the THERAMINI™ 3C brand clinical stimulator/ultrasound combination unit manufactured by Rich-Mar Corporation. However, the device disclosed in the Cody '623 Patent utilizes ultrasound signals for therapeutic purposes, and is not equipped for diagnostic purposes. In addition, the device is not portable; and, therefore, its ease of use in a clinical setting is limited.
Until now, there is no current device that effectively locates a myofascial trigger point. As a result, this has contributed to ignoring muscles as a major cause of most common pain problems and, unfortunately, has led to unnecessary testing, injections and medications, and surgeries. Accordingly, there is a need for a device that can accurately diagnose and locate trigger points, which is portable and ergonomically designed.